Simon Pietrovich was a friend and supporter of Ebenezar McCoy, Joseph Listens-to-Wind and Martha Liberty and on the Senior Council. McCoy expected Pietrovich to potentially support Ebenezar's bid to keep Harry Dresden's wizard status in the White Council conclave of Wizards held in Chicago.
He was killed in the attack by the Red Court on Archangel. His tower was a fortress. The Wardens suspect that someone let the killers in. Half a dozen Red Court nobles were killed. His Death curse took a heavy toll on his attackers though no one in the household survived.
In the series
In Blood Rites, Ebenezar McCoy says he set the Russian satellite to take out Casaverde, Paolo Ortega's stronghold, because Ortega killed Simon, who was his friend, and was going to continue to try to kill Harry Dresden.